Screening and confirmatory methods for the determination of melamine in cow’s milk and milk-based powdered infant formula: Validation and proficiency-tests of ELISA,HPLC-UV,GC-MS and LC-MS/MS

In recent years, two adulteration incidents concerning the addition of melamine, a small polar compound which is very rich in nitrogen, to pet food and infant formula products have occurred in China. These issues prompted private as well as governmental laboratories to develop methods for the analysis of melamine and related compounds in a wide variety of food products and ingredients. The development of methods was focussed on both, screening and quantification purposes, ranging from highly sophisticated chromatographic-mass spectrometric techniques to immuno-selective assays. The present work describes two screening and two confirmatory methods dedicated to the determination of melamine in cow’s milk and milk-based powdered infant formula. Screening methods are enzyme-linked immunosorbent assay (ELISA) and liquid chromatography coupled to ultraviolet detection, while confirmatory methods are based on gas and liquid chromatography coupled mass spectrometry techniques. Performance and validation data of the four methods, and results obtained in the frame of internal and European proficiency-tests are shown.     

Review of Trouble déficit de l'attention avec ou sans hyperactivité.

Reviews the book, Trouble déficit de l'attention avec ou sans hyperactivité (Attention deficit disorder with or without hyperactivity) by Olivier Revol and Vincent Brun (2010). Professionals from different disciplines discussed “Attention Deficit Disorder With and Without Hyperactivity (ADDH): from theory to practice” at Montpellier in March 2010. The resulting book by specialists in the field, led by Revol and Brun, aims to help caregivers, parents and teachers to recognize, support and assist people with ADDH. The nine chapters form an introduction to the disorder, related comorbodity and diagnostic evaluation, and address possible interventions. The conflicting opinions of professionals from psychiatry, psychology, neuropsychology and psychomotility may confuse some readers. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Experimental methods in chemical engineering: Rheometry

Rheometry is an experimental technique that measures the relationship between stresses, strains, and their derivatives of fluids and deformable materials. Capillary and Couette viscometers were among the first instruments used to study rheology but now sophisticated shear and extensional rheometers are widely available for quality control, research, and product development. Here, we introduce the basics of rheology, define material functions, and describe conventional instruments, physical principles, applications, and uncertainties. In 2016 and 2017, the Web of Science indexed 8400 articles that mention rheometry and a bibliometric map assigned the keywords into five clusters of research: behaviour and viscosity, mechanical properties and morphology, rheological properties and microstructure, polymers and nano-particles, and visco-elastic properties and mixtures. Journal of Rheology, Construction Building Materials, Food Hydrocolloids, Soft Matter, Rheologica Acta, and Journal of Applied Polymer Science publish at least 80 articles per year that mention rheometry.     

An Estimate of the Fractal Index Using Multiscale Aggregates

We study a family of estimators of the fractal index of a Gaussian process based on the quadratic deviations at different aggregation scales. The estimators are convergent and asymptotically Gaussian when suitably normalized. Confidence intervals are provided. These asymptotic results hold for a large family of stationary-increment models including fractional Brownian motions with square-integrable spectral density. The estimates are applied to the analysis of an electrical signal     

New Amino‐Acid‐Based β‐Phosphorylated Nitroxides for Probing Acidic pH in Biological Systems by EPR Spectroscopy

There is increasing interest in measuring pH in biological samples by using nitroxides with pH‐dependent electron paramagnetic resonance (EPR) spectra. Aiming to improve the spectral sensitivity (Δa_X) of these probes (i.e., the difference between the EPR hyperfine splitting (hfs) in their protonated and unprotonated forms), we characterized a series of novel linear α‐carboxy, α′‐diethoxyphosphoryl nitroxides constructed on an amino acid core and featuring an (α or α′)‐C?H bond. In buffer, the three main hfs (a_N, a_H, and a_P) of their EPR spectra vary reversibly with pH and, from a_P or a_H titration curves, a two‐ to fourfold increase in sensitivity was achieved compared to reference imidazoline or imidazolidine nitroxides. The crystallized carboxylate 10 b (pK_a ≈3.6), which demonstrated low cytotoxicity and good resistance to bioreduction, was applied to probe stomach acidity in rats. The results pave the way to a novel generation of highly sensitive EPR pH markers.     

Intégration de questions socialement vives (QS) en cours de biologie par des enseignants et enseignantes du collégial et du lycée

Résumé

Les percées récentes dans le domaine des biotechnologies permettent d’envisager l’intervention dans la production des êtres vivants en manipulant le matériel génétique. Or, cette capacité soulève des controverses à grande portée sociale. Qu’il s’agisse d’utilisation de cellules souches ou des OGM, la biologie contemporaine soulève de questions vives en lien avec les enjeux éthiques qu’elle recèle. Mais qu’en disent les enseignantes et enseignants de biologie ? Cet article présente des résultats de recherche obtenus lors d’entretiens biographiques de six enseignants et enseignantes de biologie au cours desquels ils ont traité de leur rapport au vivant. Ces résultats suggèrent que ces derniers s’intéressent à ces questions et qu’ils les prennent en charge de différentes façons malgré certaines contraintes, notamment curriculaires.     

Screening of 23 β-lactams in foodstuffs by LC–MS/MS using an alkaline QuEChERS-like extraction

A fast and robust high performance LC–MS/MS screening method was developed for the analysis of β-lactam antibiotics in foods of animal origin: eggs, raw milk, processed dairy ingredients, infant formula, and meat- and fish-based products including baby foods. QuEChERS extraction with some adaptations enabled 23 drugs to be simultaneously monitored. Screening target concentrations were set at levels adequate to ensure compliance with current European, Chinese, US and Canadian regulations. The method was fully validated according to the European Community Reference Laboratories Residues Guidelines using 93 food samples of different composition. False-negative and false-positive rates were below 5% for all analytes. The method is adequate for use in high-routine laboratories. A 1-year study was additionally conducted to assess the stability of the 23 analytes in the working standard solution.     

Foods protected by the important biological antioxidant: Uric acid

Uric acid has been proposed as an antioxidant in biological fluids especially in humans. It is shown that uric acid can be used effectively to protect food and model food preparations against oxidation. Precooked cereal flakes and food emulsions were stabilised with varying levels of uric acid.